Loud speaker



Aug. 29, 1933. M. E. PARADISE 1,924,803

LOUD SPEAKER Filed July 14 1930 Fawn-Mmmm .SUFFEVEDHND Cosmo Wmv Mun/QE ar'pPH/rsfwo Pan/05950 ORNEY Patented Aug. Z9, 1933- v PATENT ori-ica LOUD SPEAKER Morris E. Paradise, Chicago, Ill., assignor to Grlgsby-Grunow Company, Chicago, Ill., a corporation of Illinois Application July 14, 1930. Serial N0. 467,8 46

Claims.

This invention relates to loud speakers, and particularly to diaphragms therefor. In the dynamic type of speaker, wherein a coil carrying voice currents is adapted to vibrate in an in- 5 tense magneticfield, it has been customary to connect such a coil to a conical diaphragm as the sound'generating means. Such'diaphragms as a rule are made of various kinds of flexible material such as fabric, leather, or the like. In the case of fabric, it is necessary that the diaphragm have a certain degree of stiffness and weight for proper operation. Thus, it has been customary to construct a diaphragm of multi-ply, loosely woven material, such as buckram, treated as follows:

The `material'is first sized with starch or similar substance and then given the desired shape by means of a hot press. After drying, it has been usual to weight the diaphragm with a metal powder applied in the form of a suspension. Thus, powdered aluminum in a suitable lacquer has been applied over the surface of such a diaphragm as by dipping the diaphragm in the lacquer, after -which the diaphragm is dried and bel comes ready for use. A diaphragm thus treated has been found to lose the metallic particles because of the tendency of the metal particles to agglomerate and flake off. This is particularly true when the diaphragm is subjected to considerable vibration, as occurs when the loud speaker is energized. I

An object of this invention is to devise a proc ess for treating a diaphragm of any flexible material so that the coating will permanently r adhere to the diaphragm surface.

Another object is to devise a diaphragm which will ,retain its coating indefinitely.

The single figure .of the drawing shows a diaphragm treated in accordance with my invention.

The diaphragm may consist of any flexible material commonly in use, but preferably consists of buckram. For dynamic speakers of the usual size made for radio receiving sets, I pre- 45 fer to have the buckram of two plies. The buckram is sized with starch and shaped in a hot press in the usualmanner. Thereafter the shaped diaphragm is dipped into a lacquer containing powdered aluminum or any other suitable metal and a lubricant. The lubricant may consist of any oil like castor oil, which will retain its fluidity indefinitely. Preferably, I use graphite in a nely divided form. I preferably mix equal parts of graphite and powdered metal, although the proportion may be widely varied Without departing from the spirit of my invention. After the diaphragm has been dipped into the suspension, it is left to dry. As a further precaution against the diaphragm having become distorted from its desired shape, I prefer to shape it again in a hot press. The diaphragm is then ready for use.

A diaphragm treated in Ithis manner has been found to retain the metal powder on its surface without flaking. Apparently, the graphite or other lubricant becomes thoroughly mixed with the metal particles and functions as'a lubricant between the particles, permitting' the various particles to move relatively to each other without substantial resistance. Furthermore, the graphite aids in weighting the diaphragm.

While I have described this invention in connection with a conical diaphragm of buckram, it is to be understood that this is merely the preferred form of the invention. It is obvious that the process may be applied to any diaphragm having any desired shape andV of any desired material which has its surface treated in order to impart weight and stiffness thereto.

4 I claim:

1. An acoustic diaphragm comprising a loosely woven material having its interstices filled with a stiifening agent and having its surface covered with a mixture of powdered metal and finely divided graphite in a suitable binder. S5

2. An acoustic diaphragm comprising a loosely. woven material having its interstices filled with a stiffening agent and having a water-proof coating on its surface containing a mixture of powdered aluminum and finely divided graphite.

3. An acoustic diaphragm comprising a conical shaped, loosely woven material having'its interstices lled with a stiifening agent and having its surface covered with a mixture of powdered metal and nely divided graphite.

4. An acoustic conical shaped diaphragm cornprising a loosely woven material having its interstices filled with a stiffening agent and its surface covered with a mixture of powdered aluminum and nely divided graphite.

5. An acoustic conical shaped diaphragm comprising a loosely woven material having its interstices filled with a stiffening agent and its surface covered with a mixture of powdered aluminum and finely divided graphite with lacquer as a binding and water-proofing agent.

MORRIS E. PARADISE. 

